1.9 VoIP / QoS Support Function
PacketiX VPN 2.0 (build 5205 and later) incorporates advanced
priority control technology (VoIP / QoS processing technology) whereby
communication packets for IP telephone such as VoIP packets in the VPN
tunnel can be transmitted at low delay and low jitter even if networks
are mixed together.
Users with a PacketiX VPN Server 2.0 Option Pack license can easily
use this function without any settings (for details on Option Pack, see
#1.3.21#).
1.9.1 What is VoIP / QoS Support Function?
Communications that demand low delay / low jitter such as VoIP
packets require priority in processing over ordinary communications
packets (such as downloading large files). A generic name for the
technology for securing bandwidth and priority control is Quality of
Service (QoS) technology. Many conventional network devices such as IP
routers and layer 3 switches support QoS.
All Ethernet frames used to receive equal processing (cueing,
transmission) in VPN tunnels configured by encapsulating packets by
TCP/IP such as PacketiX VPN 2.0.
New technologies incorporated into PacketiX VPN2.0 realize QoS
processing for communication using layer 2 VPN configured by PacketiX
VPN 2.0. Concerning the various packets flowing through the VPN tunnel,
by automatically conducting priority control and securing bandwidth
according to priority information, communication packets demanding low
delay and jitter such as VoIP can be given priority for VPN transmission
over other packets.
Sound quality can be dramatically enhanced when using IP telephone
via VPN or when networks are mixed for traffic such as file download,
etc., by this technology.
As a technology that can provide high-priority marked packets such as
VoIP packets with priority for transmission when physical networks are
congested by VPN software for emulating layer 2 (Ethernet layer),
encapsulating by TCP/IP and transmitting, the technology developed by
SoftEther Corporation is recognized as the first with commercial
viability (as of July 2006, according to a study conducted by SoftEther
Corporation; concerning VPN software capable of realizing VPN
communication by encapsulated TCP/IP packets by emulating layer 2
[Ethernet]).
1.9.2 Applying to Extension System by Connecting Bases by Layer 2
VPN Using IP Telephone Equipment
If this function is used, even if there is normally a large amount of
communication packets (file download, etc.) flowing through VPN, VoIP
packets for telephone and so on can be provided with high priority for
transmission within VPN, thereby dramatically enhancing sound quality
when using IP telephone via VPN. This function can be used regardless of
hardware such as the router in the physical network in which the
communication packets are flowing supports QoS.
Using layer 2 VPN such as PacketiX VPN 2.0 enables you to connect
multiple separate LANs and create a single network. (for details, see
「10.5 Setting Up a LAN-to-LAN VPN (Using Bridge Connections)」 and 「10.6 Setting Up a LAN-to-LAN VPN (Using IP Routing)」). If the VoIP / QoS support function is furthermore
used, because communication for IP telephone (VoIP packets) is always
given higher priority than other traffic for bands, even if the network
is congested with traffic other than IP telephone, you can construct an
IP telephone extension system that overlaps bases at low cost. In this
case, even if there is no equipment supposed to be used on VPN such as
IP telephone equipment or VoIP gateways, if the priority control header
is properly set for packets to be sent, priority control is
automatically conducted on VPN without requiring an special operation by
end users.
Thus a high quality IP telephone system can be built using low-cost
broadband connection, which ties into reduction of communication cost,
hardware expense and administration cost.
If the priority control header is properly set for other IP packets
to be sent and received by an existing teleconference system, the
packets can be automatically provided with high priority for
transmission with the VPN by the VoIP / QoS support function.
Fig. 1-9-1 VoIP communication among bases using VPN |
1.9.3 If VoIP / QoS Support Function can be Used
If using PacketiX VPN Server 2.0 not equipped with PacketiX VPN 2.0
software or Option Pack, the VoIP / QoS function cannot be used.
With the exception of the case where the VoIP / QoS support function
is disabled by security policy on the VPN Server side, or is disabled by
connection setting on the VPN Client or VPN Bridge side (side that
initiates VPN connection), the VoIP / QoS support function is
automatically enabled for VPN communication.
With VPN sessions, you can check whether the VoIP / QoS support
function is functioning effectively by acquiring the connection status
of the VPN session. For details, see 「3.4.5 Session Management」 and 「4.5.2 Checking the Connection Status」.
1.9.4 Types of Packets Priority Controlled by VoIP / QoS Support
Function
VoIP / QoS support function checks the value of the priority rank
header in the IP packet, and if the value is to be priority controlled,
it as marked as such and priority control is executed.
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